Entrained gases i n t he cool ing s ys tem escape t hrough the t hermal control modul e degas l ine t o t he cool ant res ervoir.
The increas ing coolant temperature is felt at t he t hermos tat , and is regi s tered on the ins trument cl us t er coolantt emperature gage vi a t he ECM and ECT s ens or s i gnal.For addit ional informat ion, refer t o: Ins t rument Clus ter (413-01 Inst rument Cl us t er, Des cript ion and Operat ion).
Engine Normal Operating Temperature
W i th the coolant t emperature increas ing, at 83°C (181°F) t he t hermos tat reacts and commences openi ng. The by-pas svalve is progres s ively clos ed. Hot coolant ret urning from t he engi ne t o t he thermal control modul e i s now all owed to pas st hrough the t op hos e connecti on to the radiator. The fl ow of hot coolant t o t he radiat or now forces cold cool ant wi thi n t heradi at or and bot t om hos e t o fl ow t o t he thermal cont rol module.
Duri ng the thermos t at opening period t here i s an i nit ial temperat ure di fferenti al of t he coolant at bot h s ides of t het hermos tat . The thermos t at react s t o t he t emperature different ial and part iall y closes , whi le t he by-pas s val ve opensfurther. The thermos t at and by-pas s valve conti nue to oscil lat e whil e t he cool ant t emperat ure i ncreas es .
At a coolant temperat ure of 91°C (196°F) t he thermost at is full y opened and t he by-pas s valve i s ful ly clos ed. The returncool ant from t he engi ne is now ful ly circul ated t hrough t he radiat or and bot tom hose. Coolant flows t hrough the radiat orfrom the RH tank t o t he LH t ank, and i s cool ed by air pass i ng through the mat ri x. Ent rai ned gas es i n the radiat or es capet hrough the connect ed degas l ine t o t he cool ant res ervoir.
The increas ed cool ant volume created by heat expans ion caus es the coolant level to ri se through t he connecti ng res ervoirhose, and i nt o t he res ervoi r.
The t emperature of the cooli ng s ys t em i s cons t ant ly moni tored by t he ECM via the ECT s ens or s i gnal. The ECM uses t heECT s ignal to control operati on of the cooling fans , and to adjus t engine fueling. The ECM al so operates t he fans i nres ponse to input s from the aut omati c t ransmis s ion oil t emperat ure s ensor, Air Condit ioning (A/C) s ys tem cont rol s wit ch,and t he A/C pres sure s ens or. For addit ional i nformati on, refer to: El ect ronic Engine Cont rols - 2.2L Di es el (303-14Electroni c Engine Controls - 2.2L Dies el, Des cript ion and Operat ion).For addit ional informat ion, refer t o: Air Condit ioning (412-01 Cli mat e Cont rol , Descripti on and Operat ion).
The cool ing fan s peed is als o infl uenced by vehicle road s peed. The ECM adjus t s the speed of t he cool ing fans tocompens ate for t he ram air effect , us ing t he CAN bus road speed s ignal received from the Ant i-Lock Brake Sys tem (ABS)module.
W hen t he engine i s s hut down, t he coolant t emperature and volume decreas e. The thermos t at st art s t o clos e as t hecool ant t emperat ure decreas es to 89°C (192°F), and is fully cl osed at 81°C (178°F). The coolant level wit hin t he res ervoi rdecreas es as coolant is drawn from the res ervoi r to replenis h the s ys tem.
Followi ng engi ne s hut down when the coolant pump i s s tat ionary, the ECM may cont inue t o operat e t he cool ing fans for apre-det ermined peri od to maint ai n engine cooling.
