A few blocks from the medical clinic where Saudi Arabia's King Khalid is undergoing tests is PJ's Auto Wash. A new portable sign in front bills the place as "The King's Car Wash."

"I told the king's staff to "just consider this your car wash," boasts Vince Capello, part-owner of the place where limousines leased by the king and his entourage of over 200 are washed free, thanks to a grateful Capello who says he's delighted his highness is in Cleveland.

Capello isn't alone. Hotel bellboys who find themselves holding $100 bills as tips are happy that the king and his friends are in town. So are wealthy suburbanities who have wanted to rent their houses to the royal family ever since news leaked that a Cleveland Heights home was to leased for $20,000 a month. (Media attention soon killed the deal.)

Suddenly Cleveland is, in effect, the unofficial capital of Saudi Arabia, and the city is in the grips of Saudi fever. Arabs dressed in Western suits, paying for goods and services in cash, have rented all available limousines, imported several more from Washington, and reserved entire floors of hotels.

The king arrived in Cleveland by private jet last Wednesday for cardioivascular tests at the renowned Cleveland Clinic. He was greeted by Chip Carter. Mayor Dennis Kucinich and his wife were in Washington appearing before the National Press Club, so they could not fulfill a Saudi request to take the queen and 19 children on tour of the city shortly after the king's arrival.

The king returned to the clinic where he underwent heart surgery in 1972, in a limousine sent to Cleveland by the White House. As he walked toward the hospital door, the king smiled and waved to several hundred spectators, then disappeared inside a wing of 30 rooms - sealed off exclusively for his use and redecorated for his arrival. That was the last the press and public saw of him.

A Camp David-like curtain of secrecy fell over the Arab presence. The hospital is forbidden to say anything about its famous patient, his family and lieutenants refuse to speak to the press, and employes at various hotels housing the royal retinue say nothing to strangers.

As a result, rumors flourish. On Monday the hospital administration finally prevailed on the Saudis to release a statement in response to an erroneous news story claiming the king was about to undergo coronary bypass surgery. After much negotiation, the hospital press office was permitted to issue a two-sentence denial.

The impact of the Saudi presence is visible in the money and logistics of housing a head of state:

In the Park Plaza Hotel, adjacent to the Cleveland Clinic, the Saudis have 81 rooms reserved at a nightly cost of $3,115. Most are about $43 each, but Prince Abdullah Bind Galewy's suite is $225 a day, which makes Princess Al-Anoud's $150-a-day suite seem like a bargain.

The newsstand of the Bond Court Hotel - one of four hotels in which the Saudis have set up camp - offers a modest display of Pierre Cardin jewelry. One day an Arab bought $1,600 worth of the stuff, almost depleting the store's stock.

A bellboy at the Bond Court showed his colleagues a tip he'd received. The 300 Swiss franc note was worth more than he'd ever expected: about $180. Since bellboys agree to share large tips, he was dismayed.

The king's chefs work with the regular kitchen staffs of the hotels, helping to prepare Arab dishes. Coffee shop menus, printed in Arabic, offer chickpea dip and lamb dishes. Their hours have been extended to accommodate the Arab custom of late dinners. Room service charges are considerable, with $50 baskets of fruit ranking as a favorite snack.

An armored car arrives at the hotels each week to pay the King's staff in cash. Mayor Kucinich says he understands that the king keeps a stack of $500 bills near his bedside for dispersal to aides as needed.

In the wealthy hunt country southeast of the city, homeowners are calling real estate brokers to offer their homes for rent.

"I don't care where I go - I'll move to a Hilton," said one homeowner who saw quick profit in the Sandis' willingness to pay big bucks for short-term luxury rentals.

On of Cleveland's premiere estates, Roundwood Manor in Hunting Valley, reportedly was offered to the Saudi's at no charge by its owner, Joseph F, Hrudka, a gasket company mogul. They appear to have accepted the offer. Once owned by the Stouffer family and later by the Fazio grocery chain family, the Georgian home sits on a hill in an exclusive residential neighborhood.

Two days ago a decorator was working to furnish the house. A limousine was parked outside, and Saudi staffers worked inside. Two new 10-speed bikes, their price tags still attached, stood at the front door. Two Western Union trucks, whose drivers were presumably installing telex facilities, were parked outside.

Secret Service agents asked Ohio Bell officials not to reveal the nature of te communication systems the Saudis enjoy, but at least two direct lines link Cleveland with Washington. Rumors of direct links to Saudi Arabia and Geneva (where the king met with Egyptian leaders prior to his arrival in Cleveland) could not be confirmed.

Other secrets include the exact medical condition of the king, how long he intends to stay in Cleveland, and just who is with him during his stay. Each day one of his princes, the country's defense minister, visits the king in the afternoon and evening. Like most of the other royalty, the prince tends to stay inside praying (five times a day as muslim law dictates), reading and chatting with his aides.

A list of reservations at one hotel reveals a number of chefs, military aides, physicians and the Saudi financier who helped bail Carter intimate Bert Lance out of his financial difficulties.

At the Park Plaza, there is a suite reserved in the name of Gaith Rashad Pharaon, a 37-year-old, cigar-puffing Harvard Business School graduate. He purchased Lance's stock in the National Bank of Georgia for $2.4 million. The name of his father, court physician and formerly doctor to the late King Faisal, is also on the list of reservations at the hotel.

Each day businessmen from the Cleveland area arrive at the hotels where the Saudis are headquartered to leave their business cards. Reportedly, the hotel managers generally throw them away.

Except for salesclerks, about the only Middle West natives who have met the Middle East visitors are bar patrons. Despite a Muslim rule against drinking, some of the Saudi aides are surprisingly open about moderate drinking.

Said one security chief as he drank a Heineken: "I believe all things come from our God. And in the Bible it says not to do anything to excess, does it not?" But he acknowledged that he would never drink in Saudi Arabia for fear of a jail sentence.

One young Saudi Arabian, an interpreter, made no secret if his dislike of Cleveland. Nursing a late Sunday afternoon brandy at the Bond Court Hotel bar, he flirted with an airline stewardess, ignoring the Cleveland Browns game on the widescreen television as he lamented the fact he wasn't still in Geneva.

His left eyebrow arched skeptically when the stewardess asked if he'd visited any discos in town. He dismissed the idea with a snort, his thick, handsome lip curling into a sneer.

As he prepared to leave for a nap he bacame charming, teasing the stewardess: If you come to Saudi Arabia with me, he said, I'll make you my second wife. But, she protested, you wouldn't spend any time with me. "The entire first week," he promised.

More practically, he suggested that his limousine pick her up at her home the next day for a grand shopping spree. He slid his hand around her neck, cradling her head, his almond eyes gazing into hers. She demurred, but finally agreed to consider a date later in the week.

The Saudi smiled and reached into his pocket to pay the bar tab. From a roll of cash, his tapered, manicured fingers gently peeled a $100 bill; it was new money, and the first hundred stuck to the others.